Two former Parramatta Eels players are accused of harbouring semi-automatic weapons and possessing more than half-a-million dollars in cash after dramatic arrests in Sydney's Centennial Park yesterday.

Chance of Aust Zika outbreak real: expert

The likelihood of an Australian outbreak of the Zika virus is "small but real", a disease expert warns, as Brazil deals with a surge in the number of babies born with birth defects linked to the mosquito-borne disease.

The department of foreign affairs is warning of the risks for Australians travelling to places where there are outbreaks, with alerts current for Brazil, Paraguay, Solomon Islands, New Caledonia and the Cook Islands.

DFAT recommends pregnant women consider deferring travel to affected areas given the seriousness of the possible risk to unborn babies.

Zika has been linked to microcephaly, a neurological disorder in which infants are born with smaller heads.

The number of suspected cases in Brazil of microcephaly increased to 3893 by January 16 from 3530 cases 10 days earlier, the country's Ministry of Health said this week.

Brazilian authorities have confirmed six cases of microcephaly where the infant was infected with the mosquito-borne Zika virus.

Meanwhile, US health officials confirmed this month a baby born with brain damage at a hospital in Oahu, Hawaii, was infected by the Zika virus.

The risk of outbreak in Australia is limited but a "real possibility", James Cook University tropical disease expert Scott Ritchie believes.

"The fact that we get dengue outbreaks means that this movement of mosquito-borne viruses does happen. So it's a real thing," Professor Ritchie told AAP.

"Somebody would travel to say Brazil, get Zika virus there and come back to Cairns, or a South American traveller who's visiting Australia is infected with Zika virus.

"If they're bitten by the mosquitoes over here, the mosquitoes get infected and can potentially transmit the virus."

Professor Ritchie said an outbreak in Australia would most likely be isolated to north Queensland where the Aedes aegypti mosquito, which has the potential to carry the virus, is found.

But too little is known about the virus to confirm the extent of a possible outbreak.

"There is a potential that there are other mosquitoes in Australia that could carry and potentially transmit Zika virus that we don't know about," Professor Ritchie said.

He has recommended health authorities be vigilant.

"If someone who has a travel history which includes South or Central America comes in with a dengue-like illness, authorities should request testing for Zika virus," he said.